Present and future of glass-ionomers and calcium-silicate cements as bioactive materials in dentistry: biophotonics-based interfacial analyses in health and disease

Contemporary dental practice in the UK. Part 1: demography and practising arrangements in 2015

Objectives

To determine, by means of an anonymous, self-reported questionnaire, the demographic profile and practising details of general dental practitioners in the UK in 2015.

Methods

A previously-piloted and validated 121-question questionnaire was distributed during 2015 to 500 dentists at UK dental meetings with a request that they complete the questionnaire and return it by post in the reply-paid envelope to the corresponding author.

Results

Three hundred and eighty-eight useable questionnaires were returned, giving aresponse rate of 77.6%. Of the respondents, 60.2% were male and 39.8% female. Theirmean age since graduation was 19.7 years. Just over half of the respondents (50.9%) replied that they were practice principals, 35.8% were associates and 10.6% were foundation dentists. A quarter of the respondents were in single-handed practices, the remainder being in a partnership or group practice. There was a mean of 4.2 dentists per practice, while the mean number of dental therapists in each practice was 0.3 and 1.2 hygienists. Regarding the first available NHS appointment in the respondents' practices for non-urgent care, 23.4% could provide this on the same day, the equivalent figure for private care being 40.1%. The mean percentage of patients receiving NHS treatment was 50%, with 33.8% receiving private treatment. Just over half of respondents considered that Care Quality Commission inspections were 'valuable for fostering patient trust and confidence in dental care.' The collected data indicated that 55.4% of respondents had an intra-oral camera, while, with regard to recently-introduced concepts and techniques, 80.4% used nickel-titanium files, 47.4% used zirconia-based bridgework and 24.9% used tricalcium silicate. Of great interest, perhaps, is the response to digital radiography/digital imaging, with the results indicating that 74.1% of respondents used this form of radiography. Regarding checking the light output of the light curing units, 53.1% stated that they did check the output, but in some cases this might be at a six-monthly interval.

Conclusion

Results from this survey indicated that NHS service provision has dropped toapproximately 50% amongst the respondents. Regarding the staffing of dentalpractices, just over half the respondents were practice principals and there was a mean of 4.2 dentists per practice. The results also indicated that UK dentists continue to be innovative in the techniques that they employ.

Oroactive dental biomaterials and their use in endodontic therapy

Dental biomaterials have revolutionized modern therapies. Untreated dental caries remains the major etiological factor for endodontic treatment, and together with a decreasing rate of tooth loss escalates the importance of continuously improving the materials used for endodontic therapies. Endodontic biomaterials are used for vital pulp therapies, irrigation, intracanal medicaments, obturation and regenerative procedures. These materials offer several functions including: antimicrobial activity, mechanical reinforcement, aesthetics, and therapeutic effects. Vital pulp therapies have seen an improvement in clinical results with an incremental approach to build on the strengths of past materials such as calcium hydroxide and calcium silicates. While sodium hypochlorite remains the gold standard for canal irrigation, numerous nanoparticle formulations have been developed to promote sustained antimicrobial action. Gutta-percha based bulk fillers remain the most common materials for root filling. However, while multiple studies focus on the development of novel formulations containing drugs, glass derivatives or ionic-, polymeric-, or drug- loaded nanoparticles, a lack of reliable and long-term clinical evidence obligates further study as experienced clinicians prefer to use what has worked for decades. This review delves in to the biochemistry of the materials to scrutinize their shortcomings, and where opportunity lies to further enhance their efficacy in endodontic practice. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:201-212, 2020.

Dental practice in the UK in 2015/2016. Part 4: changes since 2002?

Objectives To determine, by means of anonymous self-report questionnaires, the changes in demographic profile, practising details and utilisation of clinical techniques/materials of general dental practitioners (GDPs) in the UK between 2002 and 2015. Method A wide-ranging, validated questionnaire, designed to elicit information on the practising arrangements and techniques and materials used, was distributed to UK-based GDPs in 2002, 2008 and 2015 with a request that they complete the questionnaire and return it by post in the reply-paid envelope to the corresponding author. Results Questionnaires were distributed by post to 1,000 UK-based GDPs in 2004 and 2008, with an additional 500 questionnaires being distributed at postgraduate meetings in 2015. Response rates of 70%, 66% and 78% were achieved, respectively. Of the respondents, 73% were male in 2002, while 67% and 60% were male in 2008 and 2015, respectively. In 2002, 65% were practice principals, falling to 51% in 2015. Regarding how patients paid for their dental care, 86% of respondents in 2002 treated patients within the NHS arrangements, compared with 57% and 50% in 2008 and 2015, respectively. The data collected in 2015 indicated that 55% of respondents had an intra-oral camera; while, with regard to recently introduced concepts and techniques, 80% used nickel-titanium files, 47% used zirconia-based bridgework, 25% used tricalcium silicate, and 17% used CAD/CAM restoration. Of great interest, perhaps, is the response to digital radiography/imaging, with the results indicating that, by 2015, 74% of respondents used this form of radiography. Conclusion Results from the three surveys indicated that NHS service provision has dropped to 50%. Regarding the staffing of dental practices, just over half the respondents were practice principals. The results also indicated that UK dentists continue to be innovative and forward-looking in the techniques that they employ.

Positive correlation between fluoride release and acid erosion of restorative glass-ionomer cements

OBJECTIVE

The aim of this study was to determine whether there is a correlation between acid erosion and fluoride release of conventional glass ionomer cements.

METHODS

Ten specimens for each material were prepared for fluoride release tests and five for acid erosion tests separately. After placed in pH cycling solution, concentration of fluoride was measured by a fluoride-ion selective electrode each day for 15 days. For the acid erosion test, specimens were immersed in a lactic acid solution and their depth measured with a spring-loaded dial gauge. The data were submitted to 3-way ANOVA, followed by Tukey's test (p<0.05) RESULTS: All materials showed ability to elute fluoride in the 15 day period of the test, with the same pattern of high fluoride release at the first 24h. Despite this, the amount of fluoride released was statistically different among the 18 groups, with the highest for Maxxion R and the lowest for Chemfil Rock (p>0.05). The highest acid erosion values were registered for Magic Glass, Ion Z, VitroFil and Maxxion R, which exceeded the maximum stipulated by the relevant ISO test (ISO 9917-1). A positive linear correlation (r²=0.4886) was found for both properties, i.e., higher fluoride release is related to higher acid erosion.

SIGNIFICANCE

Acid erosion and fluoride release are related properties of GICs, though factors such as pH and P/L ratio lead to differences between actual values for individual brands of these materials.

Effects of Polyacrylic Acid Pre-Treatment on Bonded-Dentine Interfaces Created with a Modern Bioactive Resin-Modified Glass Ionomer Cement and Subjected to Cycling Mechanical Stress

OBJECTIVES

Resin-modified glass ionomer cements (RMGIC) are considered excellent restorative materials with unique therapeutic and anti-cariogenic activity. However, concerns exist regarding the use of polyacrylic acid as a dentine conditioner as it may influence the bonding performance of RMGIC. The aim of this study was to evaluate the effect of different protocols for cycling mechanical stress on the bond durability and interfacial ultramorphology of a modern RMGIC applied to dentine pre-treated with/without polyacrylic acid conditioner (PAA).

METHODS

The RMGIC was applied onto human dentine specimens prepared with silicon-carbide (SiC) abrasive paper with or without the use of a PAA conditioner. The specimens were immersed in deionised water for 24 h then divided in 3 groups. The first group was cut into matchsticks (cross-sectional area of 0.9 mm2) and tested immediately for microtensile bond strength (MTBS). The second was first subjected to load cycling (250,000 cycles; 3 Hz; 70 N) and then cut into matchsticks and tested for MTBS. The third group was subjected to load cycling (250,000 cycles; 3 Hz; 70 N), cut into matchsticks, and then immersed for 8 months storage in artificial saliva (AS); these were finally tested for MTBS. The results were analysed statistically using two-way ANOVA and the Student⁻Newman⁻Keuls test (α = 0.05). Fractographic analysis was performed using FE-SEM, while further RMCGIC-bonded dentine specimens were aged as previously described and used for interfacial ultramorphology characterisation (dye nanoleakage) using confocal microscopy.

RESULTS

The RMGIC applied onto dentine that received no pre-treatment (10% PAA gel) showed no significant reduction in MTBS after load cycling followed by 8 months of storage in AS (p > 0.05). The RMGIC⁻dentine interface created in PAA-conditioned SiC-abraded dentine specimens showed no sign of degradation, but with porosities within the bonding interface both after load cycling and after 8 months of storage in AS. Conversely, the RMGIC⁻dentine interface of the specimens with no PAA pre-treatment showed no sign of porosity within the interface after any of the aging protocols, although some bonded-dentine interfaces presented cohesive cracks within the cement after prolonged AS storage. However, the specimens of this group showed no significant reduction in bond strength (p < 0.05) after 8 months of storage in AS or load cycling (p > 0.05). After prolonged AS storage, the bond strength value attained in RMGIC⁻dentine specimens created in PAA pre-treated dentine were significantly higher than those observed in the specimens created with no PAA pre-treatment in dentine.

CONCLUSIONS

PAA conditioning of dentine prior to application of RMGIC induces no substantial effect on the bond strength after short-term storage, but its use may increase the risk of collagen degradation at the bonding interface after prolonged aging. Modern RMGIC applied without PAA dentine pre-treatment may have greater therapeutic synergy with saliva during cycle occlusal load, thereby enhancing the remineralisation and protection of the bonding interface.

Influence of Nd:YAG laser on the penetration of a bioceramic root canal sealer into dentinal tubules: A confocal analysis

OBJECTIVE

The aim of this in vitro study, is to evaluate the penetration of a bioceramic root canal sealer into dentinal tubules at 3 mm and 5 mm from the apex after Nd:YAG laser irradiation.

METHODS

Forty freshly extracted human mandibular premolars were prepared using Reciproc® and irrigated with 17% ethylenediaminetetraacetic acid (EDTA). Teeth were divided into 4 groups: group 1, obturated with control sealer (AH Plus®); group 2, obturated with bioceramic sealer (Endosequence BC Sealer®); group 3, Nd:YAG laser + control sealer (AH Plus®); and group 4, Nd:YAG laser + bioceramic sealer (Endosequence BC Sealer®). The samples were transversely sectioned 3 mm and 5 mm from the apex and examined using confocal laser scanning microscopy. Two parameters were measured: 1) sealer penetration into dentinal tubules of the root canal and 2) sealer penetration into the perimeter of the root canal walls.

RESULTS

Penetration analysis showed that bioceramic sealer had a higher penetration at depths of 3 and 5 mm than that of the control sealer, regardless of laser use (p <0.05). Perimeter analysis showed that there was no difference between both sealers at a depth of 3 mm (p <0.05), regardless of laser use. At a depth of 5 mm, bioceramic sealer and laser showed a greater perimeter of penetration (p <0.05) than the control sealer.

CONCLUSION

The use of Nd:YAG laser did not compromise the penetration of bioceramic sealer into dentinal tubules of root canals at 3 mm and 5 mm from the apex.

The push-out bond strength of calcium silicate-based endodontic sealers

Background

The aim was to compare the dislodgement resistance of calcium silicate-based sealers (Total Fill BC Sealer, Endo CPM Sealer, BioRoot RCS) with an epoxy resin-based sealer (AH Plus).

Methods

The root canals of 80 single-rooted human teeth were instrumented with F360 up to size 45.04. All canals were obturated using matching gutta-percha cones according to the single-cone technique in combination with one of the mentioned sealers (n = 20 per group). After eight weeks of incubation (37 °C, 100% humidity), the roots were embedded in resin. Starting with a distance of 7 mm from the apex, four slices of 1 mm thickness were cut. Dislodgement resistance was measured using a universal testing machine and the push-out bond strength was calculated. Specimens were examined under 4×-magnification to determine the mode of bond failure. Statistical analysis was performed using ANOVA and Student-Newman-Keuls-test.

Results

Regarding the pooled data of all sections, the push-out bond strength of AH Plus was significantly higher than the push-out bond strength of all calcium silicate-containing sealers (P < 0.05). Out of all calcium silicate-based sealers, Total Fill BC Sealer showed the highest push-out bond strength (P < 0.05). BioRoot RCS had significant higher push-out bond strength than Endo CPM Sealer (P < 0.05). Nearly the same results were found for all four sections. BioRoot RCS only differed significantly from Endo CPM Sealer in the third section (P < 0.05).

Conclusions

The push-out bond strength of the investigated calcium silicate-based sealers was lower than of AH Plus. Total Fill BC showed the highest push-out bond strength of the calcium silicate-based sealers.

In vitro mechanical stimulation facilitates stress dissipation and sealing ability at the conventional glass ionomer cement-dentin interface

OBJECTIVE

The aim of this study was to evaluate the induced changes in the chemical and mechanical performance at the glass-ionomer cement-dentin interface after mechanical load application.

METHODS

A conventional glass-ionomer cement (GIC) (Ketac Bond), and a resin-modified glass-ionomer cement (RMGIC) (Vitrebond Plus) were used. Bonded interfaces were stored in simulated body fluid, and then tested or submitted to the mechanical loading challenge. Different loading waveforms were applied: No cycling, 24 h cycled in sine or loaded in sustained hold waveforms. The cement-dentin interface was evaluated using a nano-dynamic mechanical analysis, estimating the complex modulus and tan δ. Atomic Force Microscopy (AFM) imaging, Raman analysis and dye assisted confocal microscopy evaluation (CLSM) were also performed.

RESULTS

The complex modulus was lower and tan delta was higher at interfaces promoted with the GIC if compared to the RMGIC unloaded. The conventional GIC attained evident reduction of nanoleakage. Mechanical loading favored remineralization and promoted higher complex modulus and lower tan delta values at interfaces with RMGIC, where porosity, micropermeability and nanoleakage were more abundant.

CONCLUSIONS

Mechanical stimuli diminished the resistance to deformation and increased the stored energy at the GIC-dentin interface. The conventional GIC induced less porosity and nanoleakage than RMGIC. The RMGIC increased nanoleakage at the porous interface, and dye sorption appeared within the cement. Both cements created amorphous and crystalline apatites at the interface depending on the type of mechanical loading.

CLINICAL SIGNIFICANCE

Remineralization, lower stress concentration and resistance to deformation after mechanical loading improved the sealing of the GIC-dentin interface. In vitro oral function will favor high levels of accumulated energy and permits micropermeability at the RMGIC-dentin interface which will become remineralized.

Enhanced bioactive properties of BiodentineTM modified with bioactive glass nanoparticles

Objective

To prepare nanocomposite cements based on the incorporation of bioactive glass nanoparticles (nBGs) into BiodentineTM (BD, Septodent, Saint-Maur-des-Fosses Cedex, France) and to assess their bioactive properties.

Material and Methods

nBGs were synthesised by the sol-gel method. BD nanocomposites (nBG/BD) were prepared with 1 and 2% nBGs by weight; unmodified BD and GC Fuji IX (GIC, GC Corporation, Tokyo, Japan) were used as references. The in vitro ability of the materials to induce apatite formation was assessed in SBF by X-ray diffraction (XRD), attenuated total reflectance with Fourier transform infrared spectroscopy (ATR-FTIR), and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis. BD and nBG/BD were also applied to dentine discs for seven days; the morphology and elemental composition of the dentine-cement interface were analysed using SEM-EDX.

Results

One and two percent nBG/BD composites accelerated apatite formation on the disc surface after short-term immersion in SBF. Apatite was detected on the nBG/BD nanocomposites after three days, compared with seven days for unmodified BD. No apatite formation was detected on the GIC surface. nBG/BD formed a wider interfacial area with dentine than BD, showing blockage of dentine tubules and Si incorporation, suggesting intratubular precipitation.

Conclusions

The incorporation of nBGs into BD improves its in vitro bioactivity, accelerating the formation of a crystalline apatite layer on its surface after immersion in SBF. Compared with unmodified BD, nBG/BD showed a wider interfacial area with greater Si incorporation and intratubular precipitation of deposits when immersed in SBF.

Biological response of commercially available different tricalcium silicate-based cements and pozzolan cement

This study evaluated four root repair materials for cytotoxicity and cell attachment in vitro. Cell viability was determined at 24 hr, 3 days and 7 days by using a 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay with material extracts. Cell adhesion was examined with a scanning electron microscope on the surface of materials at 24 and 48 hr. Angelus MTA displayed the lowest cell viabilities at all-day incubations. Endocem had high biocompatibility on the first day. After culturing for 3 days and 7 days, the cell viabilities of Biodentine, Endocem and MM-MTA had similar results, and their cell viability was significantly higher than that of Angelus. No definite relation was found between the incubation time and the relative cell viability in any group. In scanning electron micrographs, the cells were attached to the material surface for all materials, although the cells in the Biodentine group were attached better than the other groups on the second day. Cell viability and cell attachment was lower in the Angelus group. Endocem, Biodentine and MM-MTA were similar in biocompatibility and cytotoxicity.

Cavity Adaptation of Water-Based Restoratives Placed as Liners under a Resin Composite

Purpose. To investigate the cavity adaptation of mineral trioxide (ProRoot MTA/MT), tricalcium silicate (Biodentine/BD), and glass ionomer (Equia Fil/EF) cements used as liners and the interfacial integrity between those liners and a composite resin placed as the main restorative material. Materials and Methods. Standardized class I cavities (n: 8 per group) were prepared in upper premolars. Cavities were lined with a 1 mm thick layer of each of the tested materials and restored with Optibond FL adhesive and Herculite Precis composite resin. Cavity adaptation of the restorations was investigated by computerized X-ray microtomography. The regions of interest (ROI) were set at the cavity-liner (CL) interface and the liner-resin (LR) interface. The percentage void volume fraction (%VVF) in the ROI was calculated. The specimens were then sectioned and the interfaces were evaluated by reflection optical microscopy, to measure the % length (%LD) of the interfacial gaps. Selected samples were further evaluated by scanning electron microscopy. Statistical analysis was performed by two-way ANOVA and Student-Newman-Keuls multiple comparison test (a = 0.05). Results. MT showed significantly higher %VVF and %LD values in CL interfaces than BD and EF (p < 0.05). No significant differences were found among the materials for the same values at the LR interfaces. Conclusions. When used as a composite liner, ProRoot MTA showed inferior cavity adaptation at dentin/liner interface when compared to Biodentine and Equia Fil.

Oral Function Improves Interfacial Integrity and Sealing Ability Between Conventional Glass Ionomer Cements and Dentin

The aim of this study was to investigate if load cycling affects interfacial integrity of glass ionomer cements bonded to sound- or caries-affected dentin. A conventional glass ionomer, Ketac Bond, and a resin-modified glass ionomer (Vitrebond Plus), were applied to dentin. Half of the specimens were load cycled. The interfaces were submitted to dye-assisted confocal microscopy evaluation. The unloaded specimens of sound and carious dentin were deficiently hybridized when Ketac Bond was used. Ketac Bond samples showed an absorption layer and an adhesive layer that were scarcely affected by fluorescein penetration (nanoleakage), in sound dentin. Nevertheless, a higher degree of micropermeability was found in carious dentin. In Ketac Bond specimens, load cycling improves the sealing capability and remineralization at the cement-dentin interface as porosity and nanoleakage was reduced. In contrast, samples treated with Vitrebond Plus exhibited a Rhodamine B-labeled absorption layer with scarce nanoleakage in both sound and carious unloaded dentin. The adhesive layer was affected by dye sorption throughout the porous cement-dentin interface. Samples treated with Vitrebond Plus had significant increases in nanoleakage and cement-dye sorption after load cycling. Within the limitations of an in vitro study, it is expected that conventional glass ionomers will provide major clinical efficacy when applied to carious-affected or sound dentin.

[Comparative in vitro evaluation of modern glass ionomer cements for adhesion strength and fluoride release]

The study proved similar adhesion strength and fluoride release level in aqueous extracts of glass ionomer cements Cemion (VladMiVa, Russia), Glassin Rest (Omega-Dent, Russia), Cemfil 10 (StomaDent, Russia) and Fuji VIII (GC Corporation, Japan). Despite of close concentrations of fluoride in glasses, the rate of fluoride release in water from calcium and calcium-barium glasses is much higher than that of strontium glasses.

Shear bond strength evaluation of resin composite bonded to three different liners: TheraCal LC, Biodentine, and resin-modified glass ionomer cement using universal adhesive: An in vitro study

Aims:

To compare and evaluate the bonding ability of resin composite (RC) to three different liners: TheraCal LC™ (TLC), a novel resin-modified (RM) calcium silicate cement, Biodentine™ (BD), and resin-modified glass ionomer cement (RMGIC) using an universal silane-containing adhesive and characterizing their failure modes.

Materials and Methods:

Thirty extracted intact human molars with occlusal cavity (6-mm diameter and 2-mm height) were mounted in acrylic blocks and divided into three groups of 10 samples each based on the liner used as Group A (TLC), Group B (BD), and Group C (RMGIC). Composite post of 3 mm diameter and 3 mm height was then bonded to each sample using universal adhesive. Shear bond strength (SBS) analysis was performed at a cross-head speed of 1 mm/min.

Statistical Analysis Used:

Statistical analysis was performed with one-way analysis of variance (ANOVA) and post hoc test using Statistical Package for the Social Sciences (SPSS) version 20.

Results:

No significant difference was observed between group A and group C (P = 0.573) while group B showed the least bond strength values with a highly significant difference (P = 0.000). The modes of failure were predominantly cohesive in Groups A and B (TLC and BD) while RMGIC showed mixed and adhesive failures.

Conclusions:

Hence, this present study concludes that the bond strength of composite resin to TLC and RMGIC was similar and significantly higher than that of BD following application of universal adhesive.

The hardness and chemical changes in demineralized primary dentin treated by fluoride and glass ionomer cement

Abstract Background Fluoride plays an important role in the control of dental caries. Aim To evaluate the chemical exchange between restoration of glass ionomer cement of high viscosity (GIC) and primary dentin with application of sodium fluoride (NaF) 2% through changes in hardness from uptake of calcium, phosphate and fluoride. Material and method Class I cavities were prepared in 40 sound primary molars, and the sample was divided into two groups (n=20) according to dentin condition: sound (1) and demineralized (2). Sub-groups (n=10) were formed to investigate the isolated action of the GIC or the association with NaF (F). This in vitro study examined the chemical exchange under two conditions, sound and demineralized dentin (pH cycling), to simulate the occurrence of mineral loss for the caries lesion. G1 and G2 received GIC restoration only; groups G1F and G2F received NaF before GIC restoration. The specimens were prepared for Knoop hardness test and micro-Raman spectroscopy. A two-way ANOVA test (α = 0.05) was used for statistical analysis. Micro-Raman data were qualitatively described. Result Increased hardness was observed in all the sites of direct contact with GIC in sound and demineralized dentin for all groups (p<0.001); no difference was observed in microhardness after application of NaF (p>0.05). In the evaluation of micro-Raman, direct contact between GIC and dentin for sound and demineralized dentin resulted in increased peaks of phosphate. Conclusion The exchange between GIC and demineralized dentin may induce changes of mechanical properties of the substrate, and uptake of mineral ions (phosphate) occurs without the influence of NaF.

Influence of Restoration Type on the Cytotoxicity of a 35% Hydrogen Peroxide Bleaching Gel

OBJECTIVES

The tooth/restoration interface may act as a pathway for hydrogen peroxide (H2O2) diffusion into the pulp chamber. Therefore, the influence of resin-modified glass ionomer cement (RMGIC) and resin composite simulated restorations on the cytotoxicity of an in-office bleaching gel was assessed in vitro.

MATERIALS AND METHODS

Cavities in enamel/dentin discs restored with RMGIC Vitremer (3M ESPE) or Single Bond/Filtek Z350 (3M ESPE) resin composite (RC) were subjected or not subjected to hydrolytic degradation (HD). A 35%-H2O2 bleaching gel was applied to simulated restored and nonrestored enamel surfaces, and culture medium in contact with the dentin substrate (extract) was collected and applied to MDPC-23 cells. Nonrestored discs subjected or not subjected to bleaching were used as positive and negative controls, respectively. Cell viability, oxidative stress, interleukin (IL)-1β expression, alkaline phosphatase (ALP) activity, and mineralized nodule deposition were evaluated. The H2O2 in the extracts was quantified. Data were subjected to statistical analysis.

RESULTS

Higher oxidative stress associated with reduced cell viability, ALP activity, and mineralized nodule deposition was observed for all bleached groups compared with the negative control group. The RMGIC/HD group, which presented the highest H2O2 diffusion, had the lowest values of cell viability, ALP activity, and mineralized nodule deposition, as well as significantly increased IL-1β expression.

CONCLUSIONS

Dental cavities restored with the RMGIC subjected to hydrolytic degradation allowed for more intense diffusion of H2O2 into the pulp chamber, intensifying the toxicity of a 35%-H2O2 bleaching gel to pulp cells.

Clinical and radiographic assessment of the efficacy of calcium silicate indirect pulp capping: a randomized controlled clinical trial

The aims of this study were to assess the effectiveness of calcium silicate cement (Biodentine) versus glass ionomer cement (GIC; control group) as indirect pulp capping materials in patients with reversible pulpitis and to compare the effectiveness of cone beam computed tomography (CBCT) versus periapical (PA) radiographs in detecting PA changes at baseline (T0) and at 12 mo (T12) postoperatively. Seventy-two restorations (36 Biodentine, 36 Fuji IX) were placed randomly in 53 patients. CBCT/PA radiographs were taken at T0 and T12. Two calibrated examiners assessed the presence/absence and increase/decrease in the size of existing PA radiolucencies under standardized conditions. The Kappa coefficient evaluated statistically the effectiveness of CBCT versus PA radiographs in detecting PA changes. Chi-square/Mann-Whitney tests were used to evaluate the association between PA changes in CBCT with various clinical measures. Significance was predetermined at α = 0.05. Clinical success rates for Biodentine and Fuji IX GIC were 83.3%. CBCT was significantly more effective in detecting PA radiolucencies compared with radiographs (P = 0.0069). Of the teeth, 65.4% and 90.4% were deemed healthy using CBCT and PA radiographs, respectively, at T12. Healing/healed rates were 17.3%/0%, while new/progressed radiolucency were 30.8%/9.6% with CBCT/PA radiographs, respectively. Seventy-one percent of healed lesions had received Biodentine; 88% of new/progressed lesions received Fuji IX GIC. Teeth presenting with an initial CBCT PA lesion had a failure rate of 63%, whereas teeth with no initial lesion had a failure rate of 16%. Although no statistically significant difference was detected in the clinical efficacy of Biodentine/Fuji IX when used as indirect pulp capping materials in patients with reversible pulpitis, CBCT showed a significant difference in that most healed CBCT lesions had received Biodentine while most that did not heal received Fuji IX. Longer-term follow-up is needed to establish their effect on the healing dynamics of PA tissues (ClinicalTrials.gov NCT02201641).

Polymer nanocarriers for dentin adhesion

To obtain more durable adhesion to dentin, and to protect collagen fibrils of the dentin matrix from degradation, calcium- and phosphate-releasing particles have been incorporated into the dental adhesive procedure. The aim of the present study was to incorporate zinc-loaded polymeric nanocarriers into a dental adhesive system to facilitate inhibition of matrix metalloproteinases (MMPs)-mediated collagen degradation and to provide calcium ions for mineral deposition within the resin-dentin bonded interface. PolymP- N : Active nanoparticles (nanoMyP) were zinc-loaded through 30-minute ZnCl2 immersion and tested for bioactivity by means of 7 days' immersion in simulated body fluid solution (the Kokubo test). Zinc-loading and calcium phosphate depositions were examined by scanning and transmission electron microscopy, elemental analysis, and x-ray diffraction. Nanoparticles in ethanol solution infiltrated into phosphoric-acid-etched human dentin and Single Bond (3M/ESPE) were applied to determine whether the nanoparticles interfered with bonding. Debonded sticks were analyzed by scanning electron microscopy. A metalloproteinase collagen degradation assay was also performed in resin-infiltrated dentin with and without nanoparticles, measuring C-terminal telopeptide of type I collagen (ICTP) concentration in supernatants, after 4 wk of immersion in artificial saliva. Numerical data were analyzed by analysis of variance (ANOVA) and Student-Newman-Keuls multiple comparisons tests (p < .05). Nanoparticles were effectively zinc-loaded and were shown to have a chelating effect, retaining calcium regardless of zinc incorporation. Nanoparticles failed to infiltrate demineralized intertubular dentin and remained on top of the hybrid layer, without altering bond strength. Calcium and phosphorus were found covering nanoparticles at the hybrid layer, after 24 h. Nanoparticle application in etched dentin also reduced MMP-mediated collagen degradation. Tested nanoparticles may be incorporated into dental adhesive systems to provide the appropriate environment in which dentin MMP collagen degradation is inhibited and mineral growth can occur.